APIS Volume 8, Number 2, February 1990
In this issue
- African Honey Bee Research in Florida
- Pesticide Paradox--Lifting Regulations and Apistan
- The Bee Breeder Publication
AFRICAN HONEY BEE RESEARCH IN FLORIDA
Last month I reported on efforts to develop an African bee plan in Florida. A large part of the projected effort will be basic research on the insect. The head of IFAS' African bee research program, Dr. Glenn Hall, and his associates continue to be busy generating information that will affect how we will deal with the invasion of the African honey bee. Research at the University of Florida focuses on honey bee deoxyribonucleic acid (DNA). DNA provides the basic blueprint for how a honey bee is constructed and behaves. DNA in the nucleus of bee cells comes from both parents at the time the egg from the queen and sperm from the drone unite. However, DNA is also found in other parts of the cell, including the energy producing capsules, called mitochondria. Because DNA from mitochondria comes only from the egg, it is inherited strictly from the queen. It is important to keep in mind the origin of specific kinds of DNA (nuclear vs mitochondrial) to fully understand and appreciate Dr. Hall's work.
The significance of Dr. Hall's research was shown by a major article published in the May, 1989 issue of Nature, one of the most widely read scientific journals. The review process leading to publication in "Nature" is strict and very few papers pass the rigors of the editors. A measure of the journal's prestige is that the discovery of DNA itself, resulting in the awarding of the Nobel Prize, was first published in its pages. The results of Dr. Hall's paper were corroborated by another authored by Deborah Smith in the same issue.
Dr. Hall's paper provides evidence that African honey bees are spread as a result of swarming by queens. Of nineteen feral colonies collected in Mexico, all had typical African mitochondrial DNA. Because only the African mother carries this kind of DNA, not one single generation of bees provided by European queens are represented in this sample. In other words, the bees have maintained their African mitochondrial DNA even when it could have been lost by only one European queen providing offspring during their journey from Brazil through Central America into Mexico.
The probability that all swarms collected by Dr. Hall would have African mitochondrial DNA should be small considering the fact that the bees are 5,000 miles and over 150 generations removed from their beginnings in Brazil. In addition, the swarms were collected only fifteen months after arrival of the African bee in the area of Mexico where collections took place, and the region still has many managed colonies of European honey bees. That every single sample had African mitochondrial DNA is extraordinary, so much so that it warranted publication in "Nature." The companion paper authored by Smith offers independent verification of Dr. Hall's results. Of a mixture of colonies and swarms from Brazil, Venezuela and Mexico, 59 out of 61 had African type mitochondrial DNA. In conclusion, the author states: "...an essentially African population is expanding...through migration and colonization of new territory by African females."
In a comment on the above papers in the same journal, Dr. Robert Page, University of California at Davis, said: " The reported demonstration of high frequencies of African-type mitochondria in honey-bee populations in South and Central America, together with Mexico, suggests an unbroken African maternal lineage for most feral bees observed." He called for more study based on both nuclear and mitochondrial DNA to provide further information on the Africanization process.
The interpretation of the above information is that drones play a much smaller role in the propagation of African bees in the tropics than do queens. If drones were the prime force causing Africanization of European bees in places like Venezuela, Costa Rica and Mexico, then there should be a greater mixture of African/European mitochondrial DNA than the above studies show. The practical significance of this is that breeding programs in the tropics relying on European drones to "dilute" African traits will not have much effect because (1) there are so few European queens to mate with, and (2) the African mother lines are continuing to produce numbers of African drones. Hybridization between European and African bees, therefore is asymmetrical in the tropics, favoring African bees. This has been observed in all places so far colonized by African bees in the Americas.
Part and parcel of this interpretation is the prediction that two populations of bees exist in areas being colonized by African bees. One population of European managed bees is constantly under threat of being Africanized by the great many wild African colonies in the area. Because the African mother lines are intact, however, the reverse is not true; very few European queens manage to produce drones which will hybridize with African queens. This means that to continue managing European stock, beekeepers must consistently requeen with European queens which must come from outside the area under siege by African bees. This is the scenario many beekeepers will face, especially in the southern U.S., with the arrival of the African bee.
The above interpretation is not without detractors. Although there have and continue to be many words said at bee meetings and other gatherings concerning the potential hybridization between European and African bees in the tropics, no reviewed publications exist to refute the findings reported above. Recently, however, Dr. Eric Mussen in "From the U.C. Apiaries, " quoted the editor of the Oregon Beekeepers' Association's Newsletter, "The Bee Line," who conducted an interview with Dr. Thomas Rinderer, USDA Research Leader on Africanized bees. In that article, the small sample size in the Smith paper was criticized. However, it was reported incorrectly as 10 bees (not hives) in Brazil and 17 or 18 bees (not swarms) in Mexico, when the correct figure was 10 hives in Brazil; 12 hives from Venezuela and 39 feral swarms in Mexico. In total, the number of both wild and managed colonies examined by investigators reported in the two articles above was 87, after subtracting out three colonies sampled in common. Dr. Rinderer was also quoted as saying that no one has looked at the parental origin of DNA, perhaps another oversight by the editor.
The first evidence for nuclear DNA differences between African and European honey bees was published by Dr. Hall in the Proceedings of the National Academy of Sciences in July 1986. This pioneering study sparked similar interest in other research laboratories around the country. Since then, Dr. Hall has given talks on the subject at state and national bee meetings, as well as the 1988 American Bee Research Conference. In the same year, he authored a full chapter describing honey bee nuclear DNA and will soon have published a major article in the journal, "Genetics," on the same subject.
According to Dr. Hall, DNA findings to date can be easily summarized.
- The migrating force of African bees consists of unbroken African mother lines spreading as feral swarms. Evidence for this is found in results of the mitochondrial DNA studies mentioned above.
- In the tropics, African queens in feral swarms have hybridized only to a small extent, if at all, with European drones. Evidence for this is found in nuclear DNA study.
- European queens in tropical apiaries extensively hybridize with African drones, and can be called "Africanized." Not only nuclear DNA evidence, but practical observation corroborates this view which is the least controversial of those mentioned here.
Therefore, as Dr. Hall pointed out in his report on DNA research funded partially by the Florida State Beekeepers Association in a recent newsletter: "As the bees move north into temperate regions, where European bees have advantages, increasing amounts of hybridization should take place. African behavior among feral bees should become reduced. European and African bees will probably establish a hybrid boundary across the southern U.S., as Dr. Orley Taylor and Dr. Marla Spivak, at the Univ. of Kansas, forecasted years ago. However, even in areas such as Florida, where European bees do survive well, feral hybrids may also survive to a greater extent than they do in the tropics."
As mentioned in last month's newsletter, as part of the Florida African Bee Plan, Dr. Hall is asking for research funding to study methods of stock identification and certification using nuclear and mitochondrial DNA. A current project focuses on controlled matings in Africanized areas. He will also be establishing baseline information and studying the African bee's dispersal patterns in Florida.
PESTICIDE PARADOX
Many are increasingly disturbed at the amount of pesticide being placed in the honey bee's environment to reduce Varroa mite populations. In response to this, regulators in Florida are under the gun to reduce movement restrictions. Current rules require all colonies in a yard to be treated before being moved, if a single mite in a roll jar is found by an inspector. Given that the economic threshold is not known and the fact that treatment at best will not kill 100% of the mites present, it seems reasonable to suggest that this is not realistic and many have called for deregulation within the state.
Unfortunately, according to Dr. Harvey Cromroy, IFAS Acarologist in charge of Varroa research, this presents a paradox. Because the only currently legal treatment using APISTAN (R) has a Section 18 emergency label, deregulation would by fiat cancel the registration. Therefore, no one would be allowed to use the product, clearly an unacceptable alternative.
THE BEE BREEDER
Many authorities acknowledge the key to better beekeeping in the future will be much more emphasis on breeding bees. The Bee Breeder, is a new publication designed to keep beekeepers informed on latest research developments and provide practical approaches to bee breeding. The premier issue includes articles on California African bee research, Brazilian beekeeping, stock importation and comb cell size. "The Bee Breeder" has a decidedly California slant and is published with support of the California Bee Breeders Association. It will be published three times a year and subscriptions are available for $5.00. Send subscriptions to 6745 Bucktown Lane, Vacaville, CA 95688.
Sincerely,
Malcolm T. Sanford
Bldg 970, Box 110620
University of Florida
Gainesville, FL 32611-0620
Phone (904) 392-1801, Ext. 143 FAX: 904-392-0190
http://www.ifas.ufl.edu/~entweb/apis/apis.htm
INTERNET Address: MTS@GNV.IFAS.UFL.EDU
©1990 M.T. Sanford "All Rights Reserved
